It is well known in the grinding machine art to dress the outside periphery of a consumable abrasive grinding wheel by several methods or forms; such as, a single point diamond, a multipoint diamond, rotary diamond, or diamond roll. The type of work being performed prescribes the dressing method which will provide optimum performance. Most automatic grinding machinery is based on the use of a relatively consumable grinding wheel, such as aluminum oxide or silicon carbide, which is periodically conditioned (trued or dressed) by a relatively non-consumable tool, such as a single-point diamond or a fixed cluster of multiple diamond points or a rotating diamond wheel (called a roll or a cutter). Since the relatively consumable wheel generally loses the ability to grind properly before it loses a significant amount of dimensional accuracy, it is generally reconditioned (dressed) before the dimensional accuracy of the workpieces is affected. Since the distance between the surface of a finished workpiece and the cutting surface of the wheel conditioning tool remains fixed, all that is required of the automatic machine is the periodic decrease of the distance between the wheel and the dresser/workpiece combination. This decrement is called "compensation" or "dress compensation". Depending on the construction of the machine, either the wheel is compensated, or the work support carries the dresser and the work support is compensated. In either case, the compensation usually takes place just prior to the wheel being passed by the dressing tool, and the dressing tool removes this amount from the wheel, leaving the relative positions of the critical surfaces of the wheel and the workpiece and the dresser essentially just as they were before compensation took place.
Modern super-abrasives, such as diamond and cubic boron nitride, are more difficult to incorporate into a fully automatic process. The problem is caused by the very property of these abrasives which makes them so attractive: their extreme resistance to wear. Wheels made of these materials wear extremely slowly and in most cases very evenly. In some applications using cubic boron nitride, the need for reconditioning of the wheel surface is demonstrated by an increase in the roughness of the finished workpiece surface. In those cases the proper remedy is to compensate a small amount, say 0.0001", and then pass the wheel by a rotating diamond cutter. This still constitutes the use of a somewhat consumable wheel and a relatively non-consumable wheel conditioning tool as described above. Initial truing of a cubic boron nitride wheel to remove eccentricity after mounting also falls in this category. However, in many applications the need for reconditioning of the wheel surface is demonstrated by a reduction in the ease with which the wheel cuts, an increase in force and temperature. The cause of these effects is the loss of "stick-out" of the individual diamond or cubic boron nitride abrasive grains beyond the material which bonds them together. The remedy is to wear or erode some of the bond material away without significantly wearing or pulling out the diamond or cubic boron nitride particles. This is accomplished by having the wheel do some grinding on some relatively soft aluminum oxide or silicon carbide, either in the form of a stationary stick or a rotating wheel. The latter is either motorized or equipped with a braking device which limits the rotational speed which the soft wheel can achieve as a result of the driving action of the super-abrasive wheel.